Solid particles separation

ABSTRACT

Apparatus and method are provided for the separation of solid particles of different weights in a liquid suspension. The suspension is flowed upwardly in a wide confined stream of shallow depth over an inclined surface having a greater inclination at one side thereof than at the other. The heavier particles move toward the side of the stream having the lesser inclination. In a preferred embodiment, the confined stream follows a curvilinear path and the greater inclination of the inclined surface is adjacent the outer edge of the curved path.

United States Patent Holm [451 Dec. 26, 1972 [541 SOLID PARTICLES SEPARATION 72 Inventor: .Thomas E. Holm, Schiller Park, in.

Assistant Examiner-Ralph J. Hill Asslgneei HPbel1 Holm, a P 'merest Attorney-Dressler, Goldsmith, Clement & Gordon [22] Filed: Feb. 16, 1971 [57] ABSTRACT {21] App]. No.: 115,640 1 Apparatus and method are provided for the separation of solid particles of different weights in a liquid [52] US. Cl ..209/l57 us nsion The uspension is flowed upwardly in a [51] Int. Cl. ..B03b 3/30 wid onfin d stream of shallow depth over an [58] Field Of Search ...209/155, 157, 460 inclined surface having a greater inclination at one side thereof than at the other. The heavier particles References Cited move toward the side of the stream having th'elesser inclination. In a preferred embodiment, the confined UNITED STATES PATENTS stream follows a curvilinear path and the greater 221,742 11/1879 Robinson ..209/157 inclination of the inclined surface is adjacent the outer 2,464,216 3/1949 Devol ..209/2ll X edge of the curved path. 2,615,572 10/1952 Hodge ......209I2ll 3,240,336 3/1966 11 Claims, 3 Drawing Figures Condolios .l ..2()9/l57 PATENTED DEC 26 I972 INVENTOR.

THOMAS E. HOLM BY 42ml, KM film 95% ATTORNEYS.

SUMMARY or THE INVENTION This invention relates to the separation of solid particles of different weights from suspensions of such particles in a liquid medium.

In the processing of ore depositsfor the recovery of valuable constituents, it is often desirable to separate particles by density difference. For particles of small size, such as the particles in sands and slimes, one method of separation by density involves the passage of a suspensionof particles down a riffled trough, or down a sluiceway which has parallel bars across its bottom. The heavier particles are trapped by the riffles or the bars while the lighter ones remain in suspension in-th'e liquid and pass out from the bottom of the trough or sluiceway.

In the present invention, asuspension of particles is moved upwardly in azwide confined stream over a surface which is tilted upward in the direction of liquid flow and upward at one side of the confined stream, the latter tilt resulting in'a greater upwardslope at one side of the confined stream than at the other.

In one embodiment of the invention, the confined stream of liquid carrying the suspended solids moves in a path which has no sidewise curvature, thereby providing uniform liquid velocity across the width of the stream. When the liquid velocity is within the desired range, the heavier suspended particles move toward the lower side of the confined stream where the upward slope is a more gradual one. When side-by-side separated portions of the confined stream are recovered, the heavier particles willbe found to be concentrated in the fraction recovered from the side of the stream having the more gradual slope and the lighter particles in the fraction recovered from the steeper side of the stream.

Control of the stream velocity is readilyobtainable by providing a hydrostatic head of suitable magnitude upstream of the lower end of the confined stream.

In another preferred embodiment, the confined stream follows a path which is curved sidewise to provide a higher liquid velocity at the outside portion of the curve than at the inside. In this embodiment, the lesser slope is on the inside portion of the curve and the heavier particles tend to move toward the inside. There is a tendency for heavier particles to move into the slower moving portion of the confined stream, as well as to the lower portion thereof; and the combination of these two tendencies results in an improved separation over that achieved where there is no sidewise curvature and no velocity differential across the stream.

In prior art systems involving downward flow over riffled or otherwise irregular surfaces, there is a tendency for heavier particles to more faster than light particles while in suspension to provide a means of separation. However, the heavier particles are slowed by contact with the bottom surface causing some remixing and resulting in a lesser efficiency of separation. In the present system involving upward flow, the tendency is for heavier particles to move more slowly than lighter particles in suspension; and contact with the bottom surface enhances this tendency and results in improved separation.

, 2 DETAILED DESCRIPTION OF THE INVENTION invention in which the confined stream follows a straight path insofar as lateral displacement is concerned.

In the embodiment of FIGS. 1 and 2, standpipe 11 is provided which has a rectangular cross section and an open end 12. Conduit 13 leads directly into open end 12 of the standpipe from a source (not shown) of a suspension of solid particles of different weights. Weir 14 is adjustable in height and determines the level of liquid in the standpipe since the total flow of liquid to the standpipe is adjusted to provide an excess of the amount of liquid which passes down the standpipe and to provide some overflow through the notch of weir 14.

The bottom of the standpipe curves to a horizontal position leading into upwardly inclined channel 16 in which separation of the particles by weight takes .place. Channel 16 is a sidewise curved channel, as best seen in FIG. 2, so that the moving stream therein changes direction and emerges from the channel at its upper end in a direction about from the direction of its entry. Channel 16-is of substantially greater width than height and is defined by outer wall 17, inner wall 18, upper wall 19, and lower wall 21.

The upper and lower walls are tilted laterally as well as in the direction of flow of the stream, so that the rise of these walls where they join the outer wall is steeper than the rise where they join the inner wall. In other words, in any cross section of channel 16 directly athwart the direction of liquid flow therein, the side of the channel adjacent the outer wall will be higher than the side adjacent the inner wall.

Lower wall 21 terminates at weir 22'and upper wall 19 terminates-at edge 23 which is above and'parallel to the weir. Both weir 22 and edge 23 are horizontal and are therefore oblique with respect to the direction of stream flow, as shown most clearly in FIG. 2.

The open end of channel 16 between edge 23 and weir 22 leads into three separate hoppers, a left hopper 24, a center hopper 26 and a right hopper 27. Hopper 24 receives effluent from the outer side of the stream containing a preponderance of light particles which pass through drain 28 for recovery. Hopper 27 receives effluent from the inner side of the stream containing a preponderance of heavy particles which pass through drain 29 for recovery. Hopper 26 receives effluent from the center of the stream containing both heavy and light particles which pass through line 31 forrecycle to the standpipe for another pass through channel 16. Pump 32, shown schematically in FIGS. 1 and 2, impels the suspension through line 31 to a level high enough to feed into the upper end of the standpipe.

In the embodiment of FIG. 3, conduit 113, standpipe 111, open end 112 and weir 114 are similar to the corresponding elements of FIGS. 1 and 2. Channel 116 is generally similar to channel 16 of FIGS. 1 and 2, except that it lacks the sidewise curvature of channel 16 so a preponderance of heavy particles on the right side of the stream and a preponderance of light particles on the left.

Bottom wall 121 terminates at weir 122 which is level and oblique with respect to the stream direction so that the'left wall 117 is shorter than the right wall of the enclosed channel. Hopper 124 collects the effluent from the left side of the channel, containing the preponderance of light particles and discharges it through drain 128. Hopper 127 collectsthe effluent from the right side of the channel'and discharges it through line 129. f

The inventiomas described above, is useful in the separation of heavy from light particles" in liquid suspension. In its usual application, it is used to separate high density particles from low density particles, but it may be used where desired to separate large particles from small particles of the same density. Maximum efficiency. in the separation of high density and low density particles will be obtained when the particles are in the same approximate size range. Useful separations can be achieved, however, in suspensionsof particles of fairly broad size distribution, as for example, sands and slimes in which about 90 percent, or more, of the particles (by weight) are between about 100 and about 600 mesh in size. The invention is useful, for example, in the concentration of non-magnetic taconite and of phosphate minerals from deposits in which they occur, and in the separation of black sands from beach sands, and slime iron ore from tailing ponds. Y

Because of its low cost and general suitability, water is the usual suspension liquid. However, other suspension'liquids may be used, particularly when such liquids are required for some other aspect 'of the overall processing.

The head of liquid applied to produce the desired velocity (the difference in height'between weirs 14 and 22, or between 114 and 122) will vary depending on the nature of the particles to be separated and other process variables. Generally, for water suspensions, a head from about l to about 24 inches is suitable, the optimum range for Lake Michigan black beach sands being from about 18 to about 24 inches and the optimum range for iron ore slimes being from about to about l9 inches. I

In one specific embodiment, a channel of rectangular cross section was constructed by cutting two onequarter (90) circular segments from Plexiglass sheet that was is inch thick. The outer radius of each was 3 feet and the inner radius was 2% feet. The two sheets were separated by a 5i: inch plastic edge and then clamped together to make an enclosed channel of rectangular cross section having a 90 turn. The channel was connected to an adjustable standpipe so that the head of fluid could be varied.

The channel was set into position by raising the discharge end to a slope of 5 inches per foot and the upper end was tilted so that the inner edge was 2% inches lower than the outer edge.

A suspension of Lake Michigan beachsand in an equal volume of water was run into the standpipe at a constant head of l9 inches above the level of the discharge end. Atthe point in the channel where the lateral tilt was about l to ll inches (2 to 3 inches per foot of width), sideways motion of the heavy black mineral particles was seen. Before the suspension reached the discharged end, complete separation of the black minerals from the silica sand was observed. Fractions of the discharge taken from the inner (lower) side of the curve showed all heavy black mineral particles and fractions of the discharge from the outer (higher) side of the curve showed all silica product.

When a slime iron ore having 96 percent by weight of particles in thelOO to 600 mesh range was suspended in an equal-volume of water and passed through the above-described apparatus at-a head adjusted to 16 inches, the inner edge fraction analyzed at-58 percent iron while the outer edge fraction had only 8 percent iron.

As may be seen from the above description, channel widths as small as 6 inches are capable of achieving effective separation. Larger widths will produce more complete separation and widths of the order of 8 to 10 feet, or more are contemplated for largecommercial installations handling large volumes of material. It is also contemplated that a plurality of the channels of this invention could be stacked, one above the other, in a commercial installation for economy of space.

The optimum range of upward slope in the direction of flow and the optimum range of lateral tilt will vary with the nature of the particles being separated, their concentration in the suspension, the velocities to be employed and other variables generally, upward slopes in the direction of flow from about 2 to about Sinches per foot of horizontal length are suitable and lateral tilts at the discharge end of the channel from about I to about 8 inches per foot of horizontal width are suitable.

The proportion of liquid in the suspension may be varied widely, the maximum solids content being limited only by the necessity to maintain free flowing characteristics in the suspension Generally, the solids content of the suspensions may vary from about 10 to about percent by volume.

The invention is applicable to both batch and continuous separation processes. It has been described with respect to its preferred modifications, but other modifications will be apparent to those skilled in the art.

lclaim:

1. A method for separating solid particles of different weights which comprises flowing a liquid suspension of said particles upwardly, in a confined stream of substantially greater width than height, over an inclined surface having a greater slope at one side of said stream than at the other, at a velocity controlled to provide slower upward flow for heavier particles than for lighter particles and separating the effluent of said confined stream into side-by-side fractions containing particles of different weights. 7

2'. A method in accordance with claim 1 wherein said particles are of relatively narrow size distribution but differ substantially in density.

3. The method of claim 1 wherein said particles are of relatively narrow density distribution but differ substantially in size.

4. The method of claim 1 wherein said confined stream flows in a path parallel to a vertical plane.

5. The method of claim 1 wherein said confined stream flows in a path defining a single sidewise curve having its outer portion at the side of said stream having the greater slope.

6. A method for separating solid particles'of different weights which comprises flowing a liquid suspension of said particles upwardly in a curvilinear curvilinear path in a confined stream over an inclined surface, said surface having a greater slope at the outer portion of said curvilinear path than at the inner portion thereof, and thereafter separating said stream into at least two sideby-side fractional streams containing suspended solids of different weights.

7. The method of claim -6 wherein said confined stream is separated into an outermost fractional stream containing the lightest particles, an innermost fractional stream containing the heaviest particles and a central fractional stream.

8. The method of claim 7 wherein said central fractional stream is recycled to said confined stream.

9. Apparatus for separating particles of different weights comprising an inclined, enclosed channel having a wide floor and shallow side walls, said floor comprising an inclined surface having a greater slope adjacent one side wall than the slope adjacent the other side wall thereof, means for supplying to the lower end of said channel a liquid suspension of particles of different weights at a controlled velocity for passage through said channel as a confined stream therein, a means for removing from the upper end of said channel sidewise spaced portions of said stream.

10. The apparatus of claim 9 wherein said side walls are straight.

11. The apparatus of claim 9 wherein said channel is curved sidewise to provide an inner side wall and an outer side wall and wherein said greater slope of said floor is adjacent said outer side wall.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION P t n N 3,707,229 Dated December 26-, 197:

Inventor(s) Thoma E. Holm It is certified that error appears in the above-identified patent and that sa id Letters Patent are hereby corrected as shown below:

Column-i, line 5-'8,more" should be -'-move- Column 5 line 9 :Eirs't occurence of. "curvilinear" should read sidewise I Signe and sealed his 15th day of May 1973.

(SEAL) v Attes tz ROBERT GOTTSCHALK EDWARD M.Fm:;TCHER ,JR. Attesting Officer Commissioner of Patents 

1. A method for separating solid particles of different weights which comprises flowing a liquid suspension of said particles upwardly, in a confined stream of substantially greater width than height, over an inclined surface having a greater slope at one side of said stream than at the other, at a velocity controlled to provide slower upward flow for heavier particles than for lighter particles and separating the effluent of said confined stream into side-by-side fractions containing particles of different weights.
 2. A method in accordance with claim 1 wherein said particles are of relatively narrow size distribution but differ substantially in density.
 3. The method of claim 1 wherein said particles are of relatively narrow density distribution but differ substantially in size.
 4. The method of claim 1 wherein said confined stream flows in a path parallel to a vertical plane.
 5. The method of claim 1 wherein said confined stream flows in a path defining a single sidewise curve having its outer portion at the side of said stream having the greater slope.
 6. A method for separating solid particles of different weights which comprises flowing a liquid suspension of said particles upwardly in a curvilinear curvilinear path in a confined stream over an inclined surface, said surface having a greater slope at the outer portion of said curvilinear path than at the inner portion thereof, and thereafter separating said stream into at least two side-by-side fractional streams containing suspended solids of different weights.
 7. The method of claim 6 wherein said confined stream is separated into an outermost fractional stream containing the lightest particles, an innermost fractional stream containing the heaviest particles and a central fractional stream.
 8. The method of claim 7 wherein said central fractional stream is recycled to said confined stream.
 9. Apparatus for separating particles of different weights comprising an inclined, enclosed channel having a wide floor and shallow side walls, said floor comprising an inclined surface having a greater slope adjacent one side wall than the slope adjacent the other side wall thereof, means for supplying to the lower end of said channel a liquid suspension of particles of different weights at a controlled velocity for passage through said channel as a confined stream therein, a means for removing from the upper end of said channel sidewise spaced portions of said stReam.
 10. The apparatus of claim 9 wherein said side walls are straight.
 11. The apparatus of claim 9 wherein said channel is curved sidewise to provide an inner side wall and an outer side wall and wherein said greater slope of said floor is adjacent said outer side wall. 